1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device including transistors having characteristics different from one another.
2. Description of the Related Art
There is a semiconductor device such as a photoelectric conversion device which includes transistors having different characteristics from one another. US2008/0029793 discusses a photoelectric conversion device in which the impurity concentration in the drain of a first transistor arranged in a photoelectric conversion region is lower than the impurity concentration in the drain of a second transistor arranged in a peripheral circuit region.
According to one aspect the impurity concentration in a gate electrode for the transistor is controlled to stably operate. However, there is no sufficient discussion in US2008/0029793 on controlling the impurity concentration in the gate electrodes of the first transistor and the second transistor.